This invention relates to apparatus and processes for the playback and monitoring of compressed bitstreams, for example MPEG1 or MPEG2 bitstreams.
A principal application of the present invention lies in the testing of MPEG or similar decoders for compliance with MPEG standards or indeed other standards or set levels of decoder performance. Forms of this invention will also find application in the testing or other investigation of MPEG and other compression encoders.
In one aspect, the object of the present invention lies in the provision of improved apparatus for the handling of compressed bitstreams, which can deal elegantly and flexibly with the demands likely to be placed on bitstream handling by a wide range of test and investigative procedures.
Accordingly, the present invention consists in one aspect in apparatus for the playback and monitoring of bit-rate reduced bitstreams, comprising buffer means for communication with bitstream storage; an interface; and a bi-directional processing array connected between the buffer means and the interface, the processing array being configurable to modify and process data flowing in a first direction in a plurality of playback modes and to analyse and process data flowing in a second direction in a plurality of monitoring modes.
In a further aspect, the present invention consists in apparatus for testing a compression decoder, comprising a store for holding compressed test data together with synthesis data defining a test picture to result from time decoding of the compressed test data; playback means for communicating the compressed test data to a decoder under test and means for comparing a decoded picture with a test picture synthesized from said synthesis data.
Preferably, the stored compressed test data includes synchronisation events for synchronisation of the decoded and test pictures.
Suitably, the stored compressed test data includes picture elements for registration of the decoded and test pictures in terms of position, level and the like.
Advantageously, a plurality of compressed test data streams correspond respectively with discrete regions of a picture enabling simultaneous execution of a plurality of tests.